DE19834805A1 - Procedure for making symmetrical laser beams of array of laser diodes with laser beams inside lens system of two lens groups influenced so beams in x-/y-direction are collimated by first/second group - Google Patents

Abstract

A procedure for making symmetrical the laser beams of an array of laser diodes in which the laser beams of a diode laser inside a lens system consisting of at least two lens groups influenced in the two coordinate directions x and y so that the laser beams in the x-direction are collimated at least by the first lens group and those in the y-direction by at least the second lens group. The laser beams of a diode laser inside a lens system consisting of three lens groups are influenced in the three coordinate directions so that the laser beams in the x-direction are collimated by the first and third lens groups and those in the y-direction by the second and third lens group.

Description

The material processing with laser beams has in the experienced an enormous upswing in the past 10 years. In particular in particular the development of diode lasers and high-performance cables Stungs diode lasers (HLDL) open up new application possibilities keiten. High-power diode lasers have a extremely compact design excellent electrical efficiency straight up and are easy to integrate into conventional Machine tools and production facilities. Because of your They are powerful (up to 2000 watts) in the Mate unthinkable. Marked are Diode laser by many individual lasers, which are in a Li are never arranged. The simple focus of this La Serstrahlles on a processing surface therefore results in a Line.

High-performance diode lasers for material processing are currently only used with direct beam transmission in laser material processing, ie an optical system is located directly in front of the laser head. However, direct beam guidance has disadvantages:

• - On the leading machine, e.g. B. a robot or egg ner portal machine, is a component of very high  hem value, namely the laser head attached. In the event of a programming error or a crash of the La serkopfes with the component or another part the laser system can cause damage in not unbe pregnant height arise.
• - The dimensions and the weight of the laser head for Direct processing restrict access to to be machined workpiece and beyond the dynamics of the leading machine also be limits.
• - The beam profile of the laser beam on the workpiece is neither homogeneous nor rotationally symmetrical, weswe it is too bad for many machining processes results or low efficiency.

So far, it has been proposed to eliminate these problems been laser beams from diode lasers through a lens to symmetrize. However, only the La focused into a two-dimensional beam, just one line (cf. Heinemann / Leininger, "Fiber coupled diode lasers and beam-shaped high-power stacks " Photonics West 1998, SPIE-Paper, 3267-13).

A lens system is also known from US Pat. No. 4,762,395 Coupling of laser light from a diode laser known which, however, is also only a two-dimensional one Focusing the laser light leads.

The basic problem that has not yet been solved with Development of systems for beam transmission of laser light consists of diode lasers, the asymmetrical  Beam parameters of the diode laser, which are in x and y Direction strongly deviate from each other, so too symmetrical that the laser beam passes through with minimal losses a rotationally symmetrical optical element (e.g. a Processing lens) can be performed.

The normal radiation field of high-power laser diodes arrays forms an elongated rectangle with a typi aspect ratio of 5: 1 (dx: dy), when used the beam ratio is the aspect ratio approx. 10: 1. The associated divergence angles have a ver Ratio of about 1:10 (wx: wy).

So far, the radiation field is either directly with "ge ordinary "i.e. spherical optics on the workpiece focused. The result is an elongated, dash shaped focus, which is only used for special applications is reversible. Alternatively, a single cylinder lens between radiation source (laser diode array) and Machining optics arranged. To get a symmetri To achieve that focus, however, cylindrical lens and Machining optics always individually adapted to each other so that no universal interface is available is.

Based on this state of the art, it is the task of present invention, a method and a device device for effective material processing with diode diode to create this originating laser light, the laser light through a rotationally symmetrical optical element to be led.  

This task is solved by creating a ver driving, with the help of which the asymmetrical beam of the Diode laser is collimated symmetrically, namely there through that the laser beams of a diode laser within one consist of at least two lens groups (x, y) the lens system in the two spatial directions x and y so influenced that at least by the first Lens group (x) collides the laser beams in the x direction be lubricated and at least by the second lens group (y) the laser beams are collimated in the y direction. A method is preferred in which the laser beams a diode laser within one of three lens groups existing lens system in the three spatial directions x, y and z are influenced such that the first and third lens group kol the laser beams in the x direction be limited and by the second and third lenses the laser beams are collimated in the y direction. This creates an interface that makes it possible light, further modules for various applications connected to the diode laser. As an example here a coupling module in a fiber optic cable and a Objective for direct machining of workpieces.

With the solution according to the invention, the known Disadvantages of direct processing with a diode laser avoided. The advantage of the invention is that Laser beam of a diode laser flexible using a Light guide cable to the respective processing point on Workpiece can be guided. So far this has not been the case possible because even small diode laser heads in industrial Weigh the approx. 10 kg version and therefore unwieldy are and hinder access to the workpiece.  

By light transmission using a light guide cable can the sensitive diode laser from machining station itself and be kept in an environment be set up, the safe operation and the usual system maintenance allowed. The invention The proposed interface optics module (SOM) is an opti system, which is an asymmetrical and divergent Radiation field in a symmetrical and collimated Radiation field transferred. The device is known characterized by a lens system consisting of three lens groups with variable focal lengths and mutually variable Ab stand, the first two lens groups from Zylin derlinsen and the last lens group from spherical Lenses exist, and being the first two lens groups together with the last group of lenses mator with connected telescope for two to each other form perpendicular directions of the radiation cross section (x and y if z is the direction of propagation). Through the nested construction becomes Lin saved, on the other hand, aberrations of the optical system can be corrected. With the focal lengths f of the three lens groups and their distance from each other there are sufficient degrees of freedom to make an asymmetry trical radiation field with the half-diameters dx and dy and the divergence angles wx and wy (each different for the directions x and y) in a symmetrical and colli emitted radiation field with the radius dz (same for x and y direction).

The advantages of the present invention can be illustrated as follows:

• - The exact collimation of the laser beam can to the interface optics module a wide range of editing lenses, oh ne that the "working distance", d. H. the distance of the Optics to the workpiece for an optimal focus position each because must be reset. this makes possible the use of lens change systems.
• - By symmetrizing the radiation field the free diameter of the connected optics optimally used, which leads to a higher working distance, smaller focus diameter or higher lei leads transmission.
• - With the symmetrization of both the divergence and also the focus diameter becomes the loss of lei performance and / or beam quality when coupling in a fiber optic cable to an absolute minimum graces.

Correcting the opening error ensures minimal possible focus diameter behind the processing object tiv, which maximizes the processing speed can be.

Further advantageous measures are in the remaining Un claims included. The invention is in the anlie illustrated drawings and will be described in more detail below described. It shows:

Figure 1 is a schematic representation of the entire system with optical fiber cable and processing optics.

Figure 2 is schematic representation of the beam guidance of the laser light of a diode laser within the interface optics module in the x direction.

Fig. 3 is schematic representation of the beam guidance of the laser light of a diode laser within the interface optics module in y-direction;

Fig. 4 is a schematic representation in cross section through an interface optics module according to the invention.

. The test arrangement shown in Figure 1 10 for coupling laser light from a diode laser to Ma terialbearbeitung shows a schematic representation of a supply unit 13 for a diode stack 12 of a diode laser whose laser light by means of a so-called interface optics module 11 and a - substantially known - downstream Fasereinkopplungsmoduls 14 is coupled into a fiber optic cable 16 . Through the glass fiber 15 , the laser light leads to a machining optics head 16 connected to a guide machine 18 , where it can be used for machining a workpiece 17 .

Fig. 2 shows a schematic representation of the beam guidance of the laser light 19 of a diode laser 12 within the interface optics module 11 in a view in the X direction; FIGS. 3, however, in the Y direction.

The interface optics module 11 (SOM) shown in FIGS . 2, 3 and 4 consists of 3 lens groups x, y and z. If laser light 19 is emitted from a diode stack 12 of a diode laser, this leads to a two-dimensional radiation field with the dimensions dx in the x direction and dy in the y direction. The laser light 19 is collimated in the x direction by the first and third lens groups x and z, and in the y direction by the second and third lens groups y and z. The definition of x-direction and y-direction is of course interchangeable.

The focal lengths fx, fy and fz and distances Sx, Sy and Sz of the lenses of the individual lens groups x, y and z are connected according to the invention by the following equations, as is also illustrated in FIG. 4 in a two-dimensional representation:

in which means:
Sx the distance of the group active in the x direction to the last group;
Sy the distance of the group effective in the y direction to the last group;
Sz the distance of the radiation source (laser diode array) to the last group;
fx the effective focal length of the (cylindrical) lens group effective in the x direction;
fy the effective focal length of the (cylindrical) lens group effective in the y direction;
fz the effective focal length of the last (spherical) lens group;
dx the radius of the radiation source in the x direction;
dy the radius of the radiation source in the y direction;
dz the radius of the collimated radiation field after the interface optics module;
wx the divergence angle of the radiation source in the x direction;
wy the divergence angle of the radiation source in the y direction.

Through the relationships according to the invention, the laser beam of the diode laser symmetrized.

Embodiment

The radiation field of a compact diode laser array has the following dimensions:

dx = 2 mm
dy = 20 mm
wx = 0.1 rad
wy = 0.01 rad

The following parameters can be selected:

dz = 12 mm
sz = 140 mm
fz = -94 mm

Using the relationships according to the invention, the distances and focal lengths of the lens groups can be found:

sx = 18 mm
sy = 68 mm
fx = 62 mm
fy = 151 mm

This results in the following optical system, characterized by the radii (of the lenses) and distances (of the individual surfaces from each other) of the lens apex:

Reference list

10th

Experimental setup

11

Interface optics module

12th

Diode stack with compacting

13

Supply for diode lasers

14

Fiber coupling module

15

glass fiber

16

Machining optical head

17th

Workpiece with machining

18th

Lead machine

19th

Laser light
X1. Lens group, cylindrical
Y2. Lens group, cylindrical
Z3. Lens group, spherical

Claims (7)

1. A method for the symmetrization of laser beams egg nes laser diode array, characterized in that the laser beams of a diode laser within a lens system consisting of at least two lens groups (x, y) in the two spatial directions x and y are influenced such that at least by the first Lens group (x) the laser beams are collimated in the x direction and at least the second lens group (y) collimates the laser beams in the y direction. 2. The method according to claim 1, characterized in that that the laser beams of a diode laser within one consisting of three lens groups (x, y, z) Lens system in the three spatial directions x, y and z be influenced so that by the first and third lens group (x, z) the laser beams in x  Direction and be collimated by the second and third lens group (y, z) the laser beams in y- Direction to be collimated. 3. The method according to claim 1 or 2, characterized in that the lenses of the individual lens groups (x, y, z) are designed in accordance with the following relationships with respect to the focal lengths fx, fy and fz and from Sx, Sy and Sz that the laser beams are symmetrized:
in which means:
Sx the distance of the group active in the x direction to the last group;
Sy the distance of the group effective in the y direction to the last group;
Sz the distance of the radiation source (laser diode array) to the last group;
fx the effective focal length of the (cylindrical) lens group effective in the x direction;
fy the effective focal length of the (cylindrical) lens group effective in the y direction;
fz the effective focal length of the last (spherical) lens group;
dx the radius of the radiation source in the x direction;
dy the radius of the radiation source in the y direction;
dz the radius of the collimated radiation field after the interface optics module;
wx the divergence angle of the radiation source in the x direction;
wy the divergence angle of the radiation source in the y direction. 4. The method according to at least one of the preceding Claims, characterized in that the laser radiate focused on a fiber optic cable and in the same to be focused and a machining device away from the laser diode array stand. 5. Device for the symmetrization of laser beams of a laser diode array ("interface optics module"), consisting of a lens system for symmetrizing and focusing laser beams, as characterized by

• 1. that the lens system ( 11 ) consists of three lens groups (x, y, z) with variable focal lengths and mutually variable distances,
• 2. the first two lens groups (x, y) made of cylindrical lenses and the last lens group (z) consisting of spherical lenses,
• 3. and wherein the first two lens groups (x, y) together with the last lens group (z) form a collimator with a connected telescope.

6. Interface optics module according to claim 5, characterized in that an end piece ( 15 ) for workpiece machining is connected to the module ( 11 ). 7. Interface optics module according to claim 6, characterized characterized in that the end piece is a light guide cable is.